Analysis systems for determining an analyte in a body fluid which use disposable test elements, test carriers, or test strips are known in the prior art. Systems of this type are used for determining the concentration of various analytes. For example, the glucose content or the cholesterol content in blood is determined.
The test elements typically contain a reagent system made of one or more reagents whose reaction with the sample liquid results in a detectable change which can be measured using the analysis system. In photometrically operating analysis systems, a color change occurs in a detection layer in the test element as a reaction of the test element with the sample, which can be photometrically measured using a measurement and evaluation unit belonging to the analysis system. For example, the intensity of the light reflected by the test element is determined.
Alternatively, so-called electrochemical analysis systems are also used, in which the dispensing of a liquid sample onto the test element results in an electrochemical reaction which is detected as a detectable charge change, current flow, or voltage change.
The known analysis systems typically operate reliably when used properly. Nonetheless, erroneous measurement results can occur as a result of application errors with the analysis instrument or the test element. Although great care is taken in the production of such analysis systems and test elements, high quality control is desirable, during which malfunctions of the measuring device are determined to avoid erroneous results.
In particular for glucose measurement systems, in which the glucose content in the blood is determined, a high quality and a low error tolerance are required. The results of the concentration determination of the glucose content in the blood are the basis for the therapy of a patient. The dosing of the insulin is determined on the basis of the determined glucose content, so that an error-free analysis value is very important. A treatment of patients which is based on an erroneous measurement result and therefore results in an incorrect dosage of insulin (too low or too high insulin dose), can result in body-threatening and life-threatening situations.
For this reason, redundant systems are used, in which, for example, two photometric detectors connected in parallel are positioned, which determine the light reflected from an analysis zone. A system of this type is described in U.S. Pat. No. 6,955,060. Alternatively, two separate analysis zones can be illuminated using two light sources to determine two different analysis results using one detector.
Error influences of analysis systems can generally have an effect on a mechanical, measurement technology, or electronic level. The digital subsystems themselves can be monitored well, but in digital-analog partial systems, a quality control to ensure measurement precision and/or correctness is significantly more difficult.
To increase the measurement precision and avoid errors in particular, multiple measurements independent from one another can be performed by a patient. For example, a user can perform two independent measurements in sequence using the same device but two different test elements. However, it is not reasonable to expect a procedure of this type for the user in practical use.
Alternatively, to increase the measurement reliability, a measurement can be performed using two devices completely independent from one another. This also results in a significantly increased measurement and cost outlay, which is not practical.
It is therefore the object of the present invention to improve the known analysis systems in such a manner that the reliability is increased.